Alterations of polyadenylate nuclease activities in herpes simplex virus-infected cells

After infection of baby hamster kidney cells (BHK) with herpes simplex virus (HSV) type 1, the incorporation rate of dThd into DNA decreases drastically and reaches a minimum 3.5 hr postinfection; later on, the incorporation rate rises again. The instant of the onset of the increase of the incorporation rate coincides with the beginning of HSV DNA synthesis. The HSV DNA synthesis was analyzed by pulse experiments with [ 3H] dThd and subsequent isolation of radio-labeled HSV DNA by isopycnic CsCl density centrifugation. The bulk of HSV DNA synthesis occurs between 5 and 9 hr postinfection. Two poly(A)-specific nucleases (endoribonuclease and exoribonuclease) were isolated, partially purified, and characterized from HSV-infected BHK cells. Both the endoribonuclease and the exoribonuclease activity increase 4.5-fold or 15-fold at the beginning of HSV DNA synthesis and decline again with the termination of HSV DNA synthesis. From these experiments we conclude that the two poly(A) -degrading enzymes probably function in the regulation of the poly(A) metabolism (posttranscriptional net polyadenylation of mRNA) during the phase of HSV DNA synthesis.